1. Technical Field
The present disclosure relates generally to operation within heterogeneous wireless systems such as, for example, hybrid network operation during which client devices can communicate using any one of several networks. More particularly, in one exemplary embodiment, the present disclosure is directed to methods and apparatus for suspending session state during hybrid cellular network operation.
2. Description of Related Technology
A wireless (e.g., cellular) network operator provides mobile telecommunications services to the public via a network infrastructure of e.g., cellular base stations (BS), base station controllers, infrastructure nodes, etc. There are a wide variety of cellular network technologies. However, historically cellular devices have been specialized for operation within a single cellular network. However, as cellular technologies have become increasingly commoditized, devices are now able to offer so-called “multimode” operation; i.e., a single device that is capable of operation on two or more cellular networks. Multimode operation allows a device to operate on any one of several network technologies, but does not enable operation on multiple network technologies simultaneously.
For example, in the last few years, Long Term Evolution (LTE) has become the dominant choice for Fourth Generation (4G) cellular network technologies. LTE is standardized under the Third Generation Partnership Project (3GPP); existing LTE networks comply with so-called Release 8 requirements, incipient research is directed to future enhancements for subsequent releases (e.g., Release 9, Release 10, etc.). Code Division Multiple Access 2000 (CDMA2000) cellular technologies are standardized under the Third Generation Partnership Project Two (3GPP2). While LTE enables significant improvements for data services, existing LTE networks do not provide adequate support for voice services; thus, 3GPP2 network operators that have deployed CDMA2000 networks will continue to use CDMA2000 for voice services, while additionally supporting LTE networks for high speed data services.
Incipient research is directed to so-called “hybrid” network operation. During hybrid network operation, the client device operates simultaneously among multiple distinct networks having different technologies. In one exemplary case, a hybrid device can support both: (i) Long Term Evolution (LTE) and (ii) Code Division Multiple Access 1X (CDMA 1X) networks; i.e., the device can maintain a simultaneous connection between a first LTE network and a second CDMA 1X network. For example, a LTE/CDMA 1X hybrid device can conduct a voice call over the CDMA 1X network while the mobile device is in LTE mode. In another exemplary case, a hybrid device can support both: (i) CDMA 1X-EVDO (Evolution Data Optimized) and (ii) CDMA 1X networks.
Existing solutions for hybrid network operation rely on the client device to manage its own operation between networks. Specifically, the client device is responsible for maintaining its active connections to the various service networks so as to minimize the required changes to existing network installations (i.e., hybrid network operation ideally will minimally affect the legacy hardware and software of the network infrastructure). Client-centric hybrid operation has several benefits. For example, there is very little (if any) infrastructure cost for the network operator. Moreover, hardware costs can be incorporated into the price of consumer devices. Additionally, hybrid network operation will not affect existing legacy devices. Similarly, devices capable of hybrid operation are also capable of normal operation.
However, since existing solutions for hybrid network operation do not require the constituent networks to coordinate with one another, the client device will inevitably experience certain scheduling collisions. For example, a mobile device with a single RF front end can be attached to a first LTE network, but it must periodically “tune out” the LTE network to perform CDMA 1X actions (such as decoding the Quick Paging Channel (QPCH) to determine if the device is being paged). Since the LTE network is unaware of the client device's tuned away operation, if the LTE network attempts to access the device and the device is repeatedly unresponsive, the LTE network will drop the connection to the device (e.g., deleting the device's current context information, and running applications). Other solutions may use more hardware; for instance, a client device that has two (2) RF front ends can simultaneously and independently connect to both technologies. However, each additional RF front end requires additional hardware, which is expensive and may impact the overall device size.
Unfortunately, extant client devices and/or networks are only configured to handle relatively short periods of poor reception. Specifically, existing LTE networks are unable to distinguish between a tune away event, and other reception loss conditions (e.g., a long deep fade, etc.). For this reason, LTE networks only resume operation when the client device is only non-responsive for a few milliseconds. For reasons described in greater detail hereinafter, short time intervals do not provide enough time to perform certain network operations.
Accordingly, there is a salient need for methods and apparatus for state suspension and/or state exchange (between devices) in hybrid radio networks.